Great question — answering as the UphillTech team:
I presume that you had XP installed on the machine and then added Windows 7, installing on an extra partition or disk. If so, then your machine will be booting off the XP installation. If you just get rid of your XP partition you will have to repair the boot system. If your two Windows installations are on separate disks, then I would just boot into Windows 7, run msconfig and delete the boot entry for Windows XP. You can then delete the stuff on the Windows XP partition, leaving only the stuff needed to boot (essentially C:\bootmgr and C:\Boot which Windows 7 will try to hide from you anyway) and anything you need to keep. This leaves you with your exising Windows 7 installation and the...
Full answer by Neal: https://superuser.stackexchange.com/a/191807 (CC BY-SA 3.0).
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